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University Library, University of Illinois at Urbana-Champaign

Plants Toxic to Animals

E

Elderberry (Sambucus canadensis)

Description

Elderberry plants are a woody shrub growing about 20 feet tall. The stems are filled with a white pith, and the leaves are opposite, pinnately compound, with lance-shaped serrated leaflets. The flowers are in small flat-topped clusters. Each flowers has about five white petals, and are about 4-6 mm in diameter. Elderberry plants also have drooping clusters of dark purple berries.

Distribution

Elderberry can be found throughout the continental United States, but is more common in the eastern to central states. It prefers moist soils and is frequently found in fields, ditches, and wooded areas. It is also cultivated as an ornamental plant or for use as an ingredient in food or as an herbal medicine.

Conditions of Poisoning

All parts of the plant are poisonous to consume, especially if wilted or in regrowth. Some cases of poisoning in humans occur from using the plant as an herbal medication. Toxicity is largely lost when the berries of the plant are cooked or fermented to make foods like jelly or wine.

Toxic Principle

Cyanogenic glycoside sambunigrin which is hydrolysed in the rumen by microorganisms to free hydrogen cyanide (HCN). The cyanide blocks the action of cytochrome oxidase that prevents hemoglobin from releasing oxygen to the tissues..

Clinical Signs 

An increased heart rate. Increased respiratory rate, panting, open-mouthed breathing, and extreme difficulty breathing. The mucous membranes are bright red. Death results rapidly from asphyxiation. 

Animals Affected

Humans, cattle, sheep, goats

References Used

Burrows, George E., & Tyrl, Ronald J. (2013). Toxic plants of North America. Hoboken: Wiley-Blackwell.

Ergot (Claviceps purpurea (Fr.) Tul.)

Description

Ergot is a fungus that lives as a parasite in the blossoms of grasses. When the grass heads are nearly mature, it appears as jumbo grains protruding from the heads. Ergot grains, which are fungus bodies and not seeds, are several to many times the size of the grass seed. They are dark violet to almost black and are curved, hard, and hornlike. Ergot varies in abundance from year to year.

Distribution

Ergot is well known as a disease of rye. It also attacks many of the wild grasses that grow along roads, in fence rows, woods, meadows, and pastures, and can often be found on wild rye, quack grass, red top, and bromegrass. It occurs throughout Illinois, being more abundant in some years than in others. 

Conditions of Poisoning

Animals get ergot either in the grain fed them or by grazing on infected grass. Obtained in either way, ergot may cause acute poisoning if a large quantity is eaten at one time. Also, because the effect of ergot is cumulative, poisoning may develop slowly if lesser quantities are eaten regularly. Experiments have shown, however, that a small amount of ergot is not injurious to dairy cattle that are amply provided with a balanced ration.

Control

Do not feed grain or hay that contains ergot. Clean contaminated grain before feeding it. Destroy infested hay. Before planting rye, clean the seed thoroughly either by mechanical means or by immersing it in a 25% salt solution. If using the salt solution, skim off ergots as they rise to the top; then wash the rye seed in water to remove the salt; dry, and plant. If wild grasses are infested, burn them to destroy the ergot.

Besides attacking many kinds of wild grasses, ergot is frequently abundant on rye in rye-fields and on volunteer rye in wheat-fields. Grain from these fields (or screenings used as feed) is very likely to cause poisoning. If there is much ergot in the grain, its effect can be very severe.

Toxic Principle

The toxic action of ergot is due to the numerous alkaloids (ergotamine, ergocristine, ergonovine, etc.) present in the sclerotia and other components--choline, ACH, histamine, sterols. Over 40 alkaloids have been identified which are derivatives of lysergic acid, some of which are inactive.

The important naturally occurring alkaloids are ergotamine and ergonovine. Of these, ergonovine is more readily absorbed. Both compounds are potent smooth muscle activators. LSD is also derived from ergot, and the smooth muscle contracting activity, although sometimes present, is not always seen. LSD causes depersonalization or hallucinations and may produce toxic psychosis.

Clinical Signs

Ergot poisoning, often called ergotism, produces two distinct types of clinical signs. Acute poisoning, which results from eating a large amount of ergot at one time, causes muscular trembling, discoordination, convulsions, and painful contraction of the muscles. In fatal cases the animal becomes delirious.

The gangrenous type of poisoning, which follows continued feeding on smaller amounts of ergot, causes the animal to become dull and depressed and to develop gangrene of the tail, feet, ears, or teats. Gangrene may vary from rather simple sores around the coronary band or top of the hoof, in the space between the claws, or on the teats to a loosening of the hoof or the sloughing of a larger part of a limb or of the tail, ears, or teats. Before sloughing occurs, a well-marked line of division can be seen between the healthy and gangrenous tissue, similar to the type of lesion that has been observed in selenium poisoning in such western states as Kansas, Nebraska, and Wyoming.

Nausea, vomiting, colic, and diarrhea may occur in both types of poisoning. Even when none of the above signs of ergotism are apparent, the presence of ergot in feed should be suspected whenever pregnant animals have an otherwise inexplicable tendency to abort.

Animals Affected

All animals and humans are susceptible to ergotism, but cattle are often the most affected.

References Used

https://beef.unl.edu/cattleproduction/ergot-poisoning-in-cattle

F

Fireweed (Kochia scoparia (L.) Schrad.)​

Description

Fireweed is known by many names including Summer Cypress, Burning Bush, and Mexican Fireweed. Fireweed can be grown in dry drought conditions. In ideal conditions, it grows to six feet high. The plant's stems have many branches with soft, fluffy leaves. The flowers are green and unnoticeable, growing in the axils of the upper leaves. The veins of the leaves, as well as mature stems, are typically red. The stems change to bright red in the fall. 

Distribution

Fireweed is found throughout the western and northern United States, as well as in much of Canada. It is common along roadsides, the edges of fields, and the edges of waste areas.

Conditions of Poisoning

Fireweed can affect many biological systems of livestock, including the cardiovascular system, respiratory system, nervous system, renal system, integumentary system, ocular system, and hepatic system. Immature Fireweed is often used in livestock's feed because it has a similar composition to alfalfa. When consumed in large quantities, mature Fireweed can cause nitrate poisoning. 

Control

Individuals should contact their local agriculture extension specialist or county weed specialist for guidance in the best practice for managing Fireweed in their area.  Herbicides tend to be less effective as Fireweed matures; their general effectiveness depends on the size of the dose used and the age of the plant. 

Toxic Principle

Toxicity of the plant can change depending on growing conditions; more mature plants or plants growing in extreme drought can be more toxic to animals. In general, Fireweed can produce nitrates, sulfates, saponins, and alkaloids. 

Clinical Signs

Livestock will show different symptoms of Fireweed poisoning depending on the biological system affected. Commons symptoms are difficulty breathing, blindness, depression, kidney failure, and liver disease. In cases of severe nitrate poisoning, livestock can die. 

Animals Affected

Sheep, horses, cattle

References Used

https://plants.usda.gov/plantguide/pdf/pg_kosc.pdf

https://csuvth.colostate.edu/poisonous_plants/Plants/Details/84

Foxglove (Digitalis purpurea L.) 

Description

Foxglove is an erect herb found as a weed or as a cultivated ornamental grown in gardens. It typically grows up to approximately 5 feet tall. The leaves are alternate and the flowers are showy, pink, and bell-shaped. Flowers grow terminally on the stem on elongated racemes.

Distribution

Foxglove currently grows in the northwest states of the United States. It prefers rich soils and commonly grows along roadsides, fences, in open clearings in the woods, and in unused areas.

Conditions of Poisoning

Poisoning occurs when the plant is eaten. Livestock are infrequently poisoned, but will eat the plant occasionally either fresh or in hay. The plant remains toxic when dried.

Control

Do not allow animals to graze in areas where foxglove is present. The plant can be removed by pulling it from the ground, although you should be careful to remove all roots and to not shake seeds onto the surrounding soil. Use a waste bag to hold the removed plants to further contain the seeds. Process may take multiple seasons to remove all traces of foxglove from the area.

Toxic Principle

Cardiac glycosides such as digoxin, digitonin, and digitoxin are in all parts of the plant. 

Clinical Signs

Symptoms of poisoning include dizziness, vomiting, diarrhea (possibly bloody), irregular heart beat, weakness, stupor, and delirium or hallucinations. Poisoning can be fatal.

Animals Affected

All animals and humans are susceptible to varying degrees.

References Used

Burrows, George E., & Tyrl, Ronald J. (2013). Toxic plants of North America. Hoboken: Wiley-Blackwell.

G

Ground Ivy (Glechoma hederacea L.)

Description

Ground ivy is a low, prostrate perennial herb with slender 4-sided stems that hug the ground, root at their joints, and often cover areas of many square feet. Its leaves, two at a joint, are raised on slender stalks. They are roundish and have scallop-like teeth on their margins. Its small bluish flowers, found in the axils of the leaves, appear from April to May and even into July.

Distribution

Ground ivy, sometimes called Creeping Charlie, is a common weed of moist shaded places and is to be found in fence rows, about farmsteads, and in woodland pastures, gardens, and wastelands. It is also frequent near streams and ditches. A native of Europe, it has become a common plant throughout Illinois. 

Conditions of Poisoning

Ground-ivy poisoning is rare, probably because most animals do not like the bitter taste of the plant. Horses, the animals usually affected, are poisoned only after eating large quantities of the plant, either green or dried in hay.

Control

Reasonable care should be taken not to graze animals in areas that are heavily infested with ground ivy, particularly at times when other herbage is dry or scarce. Neither should hay be made in meadows where the plant is abundant. Ground ivy should be regarded as a weed and destroyed in all places where it is a danger to animals. It is easily destroyed by cultivation.

Toxic Principle

Like other members of the mint family, ground ivy contains a volatile, aromatic oil. It also contains a bitter substance of unknown chemical constitution. It is collected as a drug plant and is used medicinally in small amounts as a stimulant and tonic. 

Clinical Signs

After having eaten large amounts of ground ivy, poisoned animals, especially horses, slobber and sweat, and the pupils of their eyes become dilated. They pant for breath as if from overstimulation. Such poisoning is rarely fatal.

Animals Affected

Horses

H

Hemp (Cannabis sativa)

Description

Hemp is a rough, odorous herb with few or no branches and angular stems that are covered in short, stiff hairs. Resources differ regarding the size of the plant, but the reported range can be from 3-12 feet tall. Lower leaves are opposite and upper leaves are alternate, and the leaves are long-stalked and palmately divided into 3-7 toothed leaflets. Flowers are small and green.

Distribution

Hemp occurs in most areas of the United States, particularly where it was originally grown for its fiber. Habitats include borders of floodplain woodlands, borders of low-lying fields, weedy meadows along rivers, fence rows, and roadside ditches.

Conditions of Poisoning

Poisoning commonly occurs when large quantities of the plant are ingested. All parts of the plant are poisonous, but the greatest toxicity is found in the flower stalks. Poisoning symptoms can also occur from inhalation of the plant.

Control

Mammalian herbivores avoid browsing hemp when other plants are available, so be sure that animals grazing in areas infested with hemp have plentiful options for food.

Toxic Principle

Resins, including Delta-9-THC (tetrahydrocannabinol) and cannabidiol.

Clinical Signs

Prolonged depression, vomiting, incoordination, sleepiness or excitation, hypersalivaton, dilated pupils, blurred vision, low blood pressure, low body temperature, seizure, coma, death (rare). Consumption of the plant may also affect the flavor and odor of the milk produced by the poisoned animal.

Animals Affected

Dogs, cats, horses

References Used

https://plants.ces.ncsu.edu/plants/all/cannabis-sativa/

https://www.aspca.org/pet-care/animal-poison-control/toxic-and-non-toxic-plants/indian-hemp-0

Knight, A. P., & Walter, R. G. (2001). A guide to plant poisoning of animals in North America. Jackson, Wyo.: Teton NewMedia.

Horse Nettle or Bull Nettle (Solanum carolinense L.)

Description

Horse Nettle grows to be about 1-2 feet tall, and has yellow spines on the stems and leaves. Both the leaves and flowers are simple, alternate, oblong, and irregularly lobed. The flowers are in clusters at the top of the plant, ranging from pale violet to white in color. The berries are about 1-1.5cm in diameter and are yellow when they're ripe. Flowers appear in June to August, are light purple to white, 3/4 to 1 inch across, and in short racemes near the top of the plant. Petals are united with 5 points at the margin. Fruits are globose, about 1/2 inch in diameter and yellow when mature. Yellow or brownish seeds are numerous, and irregularly circular, about 1/8 inch across. 

Distribution

Horse Nettle is found throughout the Southern United States, as well as parts of the Midwest and Northeastern states. In particular, it is a perennial weed of disturbed soils and unused areas along roads and field edges, especially of the southern States. It is a common weed in all counties of Illinois.

Conditions of Poisoning

Poisoning occurs primarily when animals are confined in overgrazed fields or where nightshade is abundant. The hazard of poisoning varies depending on the plant species, maturity of plants, and other conditions. Generally, the leaves and green fruits are toxic. Ingestion of juice from wilted leaves may be especially toxic and sometimes deadly. Many cases of poisoning have been reported as a result of eating green berries. Green berries have produced severe intestinal, oral and esophageal lesions in sheep. Cattle reportedly seek out the berries of Solanum species and will eat the green plant, specially when other green forage is unavailable.

Control

Animals should be kept away from fields with heavy infestation of nightshade. Plants should be mowed or pulled up while in flower, and burned. Remove green parts of potatoes before cooking, eat only ripe tubers.

Toxic Principle

Tropane alkaloids, especially solanine, which has similar effects as atropine on the autonomic nervous system. Also directly irritating to the oral and gastric mucosa. Green plant and unripe fruits are the most toxic. Toxicity is reduced by drying.

Clinical Signs

Nausea, vomiting, salivation, drowsiness, abdominal pain, diarrhea, weakness, respiratory depression; may be fatal.

Animals Affected

Horse, cattle, goats, sheep, pigs, rabbits

References Used

https://plants.ces.ncsu.edu/plants/all/solanum-carolinense/

Horsetails (Equisetum arvense L.)

Description

Herbaceous, perennial, leafless plants with hollow stems that readily separate at the nodes. The leaves are reduced to papery scales with black tips that surround the stems at each node. The stems are cylindrical, ridged and rough to the touch owing to the high silicate content. There are two types of stem, fertile and infertile. Fertile stems are unbranched, and are tipped by a cone-like structure containing spores. Infertile stems have multiple whorled branches at the nodes. The plant reproduces from a deeply buried rhizome and from terminal spore bearing cones. (Colorado State University's Veterinary Teaching Hospital's Guide to Poisonous Plants)

Distribution

Horsetail is a weed that grows in sandy soils in fields, ditches along roads, and along the banks of rivers. There are six species growing in North America, and they tend to prefer cooler, moist growing conditions. 

Conditions of Poisoning

Plants are toxic at all stages and remain toxic when in hay. Young horses are most susceptible to Equisetum poisoning. Plant is rarely eaten except when dried in hay. Hays containing 20% horsetail or bracken fern will result in thiamin-deficiency symptoms in 2-5 weeks.

Control

Animals suspected of being poisoned by horsetail varieties should be taken off of hay or pasture containing the plant and fed a nutritious diet that includes cereal grains rich in thiamine. Treatment with a large dose of thiamine hydrochloride (3-5 mg per kg of body weight) intravenously followed by several days of thiamine intramuscularly (1-2 mg per kg of body weight) provides rapid recovery and restores thiamine levels to normal.

Toxic Principle

Thiaminase is the suspected toxin. Also contains aconitic acid and polustrine, and silicates. All species of Equisetum should be considered potentially toxic to animals until proven otherwise. 

Clinical Signs

Initial weight loss followed several weeks later by incoordination of the hind legs. Diarrhea may also occur before the onset of weight loss and incoordination. Affected animals become progressively weaker and eventually recumbent, and staggers and tremors may be seen. Serum pyruvate levels increase while thiamin levels are depleted. Once horses are down and cannot get up, they usually die within 1 to 2 weeks. Cattle poisoned with horsetail generally show weight loss, decreased milk production, diarrhea, and hyperexcitability.

Animals Affected

Horses, cattle, sheep

Resources Used

Knight, A. P., & Walter, R. G. (2001). A guide to plant poisoning of animals in North America. Jackson, Wyo.: Teton NewMedia.

Hyacinth (Hyacinth orientalis)

Hyacinth blossomsDescription

Hyacinth is one of all the early spring blooming flowers most favored by home gardeners. It is a bulbous herb

Hyancinth Bulbsof the lily family with its origin in the Mediterranean region and cultivated in many color varieties. Green leaves, 7-8 per bulb, all arising from the ground level, are fleshy, glossy, narrow with smooth margins, 4-12 inches long and about 3/4 inches wide without marginal teeth. Flowers, borne in a dense raceme on a 6-8 inch long stem, are bell-shaped, and eventually open into 6 reflexed tepals. The flower is most well known for its fragrance. Fruits are globose and have 3 divisions. The bulb is 1-1/2 to 2 inches in diameter, light purple or cream colored, and covered with dry skin-like layers.

Distribution

Hyacinths are often potted and grown inside or grown outdoors in gardens.

Conditions of Poisoning

The poisonous principle is concentrated in the bulb. Ingesting only a small amount of the bulb may cause stomach upset. Keep the bulbs out of the reach of animals, particularly dogs, cattle, and pigs. Other plant parts are also poisonous, but are less concentrated than in the bulb.

Toxic Principle

Contains calcium oxalate raphides in what appears to be ejector cells (similar to Araceae plants) and alkaloids such as lycorine. Both bulbs and plants may be irritating to the skin and gastrointestinal tract.

Clinical Signs

Hyacinth poisoning is very rare. Clinical signs usually include digestive tract disorders such as colic, vomiting and diarrhea. Skin irritation from contact is possible, although usually minor. Allergic asthma and nasal irritation in susceptible individuals.

Animals Affected

Dogs, cattle, pigs, cats, horses

References Used

https://plants.ces.ncsu.edu/plants/all/hyacinthus-orientalis/

Hydrangea (Hydrangea spp.)

Pink Hydrangea blossomDescription

The cultivated species, Hydrangea macrophylla Ser. (= H. hortensis), is a deciduous shrub which can reach nearly 6 feet. The common cultivated species is grown widely in gardens and as potted plants. The flowers among the cultivated species include white, pink, mauve, bluish purple, to blue. The forms of the flower clusters and the leaves of the cultivated species are similar to those of the cold-hardy wild species (H. arborescens L.).

Wild hydrangeas, H. quercifolia Bartr. and H. arborescens L., are shrubs which reach from 3.5 to 10 feet in height. The stems are light green when new, turning light brown and woody with time. Leaves are alternate, 4-10 inches in length, dark green above, lighter or pale green on the underside. The leaves of H. quercifolia Bartr. are deeply lobed, while those of the other species (H. arborescens L.) are broadly rounded with apex tapering to a point. Flowers appear in clusters or heads, mostly with 4 petals in white or cream color, blooming from June to July. The capsular fruit is less than 1/8 inch in length and has many small, thin brown seeds.

Distribution

Though wild hydrangeas are sometimes grown as ornamental shrubs in gardens, H. arborescens L. is widely distributed in wooded areas, rarely in full sunlight, from New York to Georgia, west to Kansas and Oklahoma including the southern half of Illinois. H. quercifolia Bartr. is limited to the southeastern states and usually grows in considerable shade on river bluffs and steep banks of sinkholes.

Conditions of Poisoning

Generally poisoning is rare and only occurs after eating large quantities of the plant, but a horse was seriously poisoned after eating a single potted hydrangea.

Toxic Principle

May contain the cyanogenic glycoside hydrangin, but cyanide intoxication is rare and poisonings do not generally involve effects or clinical signs of typical cyanide.

Clinical Signs

Affected animals may experience painful gastroenteritis, and diarrhea which may be bloody.

Animals Affected

Dogs, cats, horses

References Used

https://www.aspca.org/pet-care/animal-poison-control/toxic-and-non-toxic-plants/hydrangea